Field of the Invention
The present invention is directed to the recovery and purification of acetonitrile from waste solvent acetonitrile. For purpose of the present application the term “waste solvent acetonitrile” shall mean a mixture of acetonitrile containing impurities such as water, isopropyl acetate, isopropyl alcohol, heptane, trimethyl silanol, hexamethyl disiloxane, methanol, benzene, n-heptanes and tetrahydofuran, acrolein, oxazole, cis and trans crotonitrile, methacrylonitrile and allyl alcohol. The relative proportions of the components of the waste solvent acetonitrile can vary over a wide range depending on various conditions. The concentration level of the organic impurities in the waste solvent acetonitrile is usually less than 25% with no single organic component found in greater than 2 to 10 wt % concentration. Typically, solvent waste acetonitrile contains between 25 and 85% acetonitrile and is free of acrylonitrile and hydrogen cyanide. Prior to the invention set forth in this application waste solvent acetonitrile was usually burned or otherwise safely disposed.
The present invention is directed to a process by which waste solvent acetonitrile free of acrylonitrile and hydrogen cyanide is treated to obtain purified acetonitrile which is recovered and sold.